1. Field of the Invention
This invention relates to exercise treadmills, and in particular to treadmills having a frame with a rear roller assembly and an endless belt in which tensioning structure associated with the rear roller tensions the endless belt.
2. State of the Art
Typical treadmills include a continuous or endless belt trained about a pair of rollers. The belt has an upper stretch which extends over a tread base which supports a user thereon. The base is secured to a frame which generally consists of a frame having two longitudinal members joined together as by cross-members or braces secured to the longitudinal members proximate the front end and the rear end of the machine. The rollers are attached to and between the longitudinal frame members. The front or rear roller may be driven by a motor.
In the operation of a treadmill, the belt may become misaligned relative to the base. The misalignment may be the result of a variety of causes including misaligned front and rear rollers.
In order to maintain the belt in the center, the pulleys may be adjusted to vary the belt tension as disclosed in U.S. Pat. No. 5,088,729. In the '729 patent, a rear roller assembly has an adjustment screw on each end cap. The adjustment screw may be tightened or loosened at both the left side and the right side to realign the rear roller and in turn to increase or decrease the tension on the belt on the left side and the right side. By correctly manipulating the adjustment screws, the belt can be tensioned so it will maintain its relative position in the center of the roller. It may be noted that adjustment is required of two adjustment screws to effect proper tensioning of the belt and to align the belt. Proper alignment and tensioning of the belt may, therefore, be difficult to achieve through misoperation of the screws.